In the E2995 study, a Phase III Multicenter trail coordinated by ECOG, patients were randomized to MEC chemotherapy with or without the PSc for refractory and relapsed AMl. Pharmacokinetic (PK) studies were and integral part of this study. A total of 144 evaluable patients were entered. PK samples have been received for 77 patients, 89 samples for analysis of the PSC level, and 585 samples for Mitoxantrone and Etoposide. The area under the curve (AUC) and other PK values will be compared in the two treatment arms.